Precise modifying method for fine particle dispersion liquid

Abstract

A method for modifying a fine particle dispersion liquid has excellent dispersibility and dispersion stability. In this method for modifying a fine particle dispersion liquid having improved fine particle dispersibility, impurities included in an agglomeration of fine particles contained in the fine particle dispersion liquid are released into the dispersion liquid by applying physical energy to the agglomeration and performing dispersion processing for dispersion into particles that are smaller than the agglomeration of fine particles. The impurities are removed from the dispersion liquid by means of a removal unit provided with a filtration membrane before reagglomeration is caused by the impurities.

The invention claimed is: 
     
       1. A method for reforming a fine particle dispersion solution, wherein the fine particle dispersion solution includes aggregate of the fine particle, and impurities comprising in-solution impurities present in the dispersion solution independent of the aggregate and in-particle impurities present in the aggregate, the method comprising the steps of:
 performing a dispersion process, comprising:
 applying a physical energy from a disperser to the aggregate of the fine particle included in the fine particle dispersion solution; 
 dispersing the aggregate of the fine particle to smaller particles compared with the aggregate of the fine particles; and 
 discharging the in-particle impurities from the aggregate into the dispersion solution, the discharged in-particle impurities becoming in-solution impurities; 
 
 transporting the dispersion solution after the dispersion process to a removing unit via a transporting path; and 
 performing a removal process to remove the in-solution impurities including the discharged in-particle impurities from the step of discharging, from the dispersion solution by the removing unit, 
 wherein the removal process to remove the in-solution impurities including the discharged in-particle impurities from the step of discharging from the dispersion solution is started by the removing unit within 3 seconds after the in-particle impurities are discharged into the dispersion solution. 
 
     
     
       2. The method for reforming the fine particle dispersion solution according to  claim 1 , wherein the dispersion process and the removal process are carried out continuously and repeatedly. 
     
     
       3. The method for reforming the fine particle dispersion solution according to  claim 1 , wherein the removing unit is equipped with a filtration membrane, and the in-solution impurities are removed from the dispersion solution by using the filtration membrane. 
     
     
       4. The method for reforming the fine particle dispersion solution according to  claim 3 , wherein the filtration membrane is an ultrafiltration membrane, and the dispersion solution is supplied to the filtration membrane to carry out filtration by a cross-flow method so that the in-solution impurities are removed from the dispersion solution. 
     
     
       5. The method for reforming the fine particle dispersion solution according to  claim 1 , wherein the dispersion process is performed by the disperser being a rotation type disperser which rotates a stirring blade in the dispersion solution, and the dispersion process is carried out with setting a circumferential velocity of the stirring blade at 10 m/sec or more. 
     
     
       6. The method for reforming the fine particle dispersion solution according to  claim 1 , further comprising controlling dispersion property of the fine particles in the fine particle dispersion solution by controlling pH of the fine particle dispersion solution obtained after the removal process. 
     
     
       7. The method for reforming the fine particle dispersion solution according to  claim 1 , wherein a primary particle diameter of the fine particle is 200 nm or less. 
     
     
       8. The method for reforming the fine particle dispersion solution according to  claim 1 , wherein the fine particle is a metal fine particle, an organic substance fine particle, or an oxide fine particle. 
     
     
       9. A method for producing a fine particle dispersion solution, comprising the steps of:
 providing a processing device comprising processing surfaces which are disposed and configured to approach to and separate from each other, at least one of the processing surfaces rotating relative to the other of the processing surfaces; 
 mixing a fine particle raw material solution including at least a raw material of the fine particle and a fine particle separating solvent including at least a fine particle separating substance to separate the fine particle in a space between the processing surfaces to form a mixed fluid; 
 separating the fine particle in the mixed fluid, forming the fine particle dispersion solution; and 
 performing the method for reforming the fine particle dispersion solution according to  claim 1 . 
 
     
     
       10. A method for reforming a fine particle dispersion solution, wherein the fine particle dispersion solution includes aggregate of the fine particle, and impurities comprising in-solution impurities present in the dispersion solution independent of the aggregate and in-particle impurities present in the aggregate, the method comprising the steps of:
 performing a dispersion process, comprising:
 applying a physical energy from a disperser to the aggregate of the fine particle included in the fine particle dispersion solution; 
 dispersing the aggregate of the fine particle to smaller particles compared with the aggregate of the fine particles; and 
 discharging the in-particle impurities from the aggregate into the dispersion solution, the discharged in-particle impurities becoming in-solution impurities; 
 
 performing a removal process to remove the in-solution impurities including the discharged in-particle impurities from the step of discharging, from the dispersion solution by a removing unit within 3 seconds after the in-particle impurities are discharged into the dispersion solution; and 
 controlling dispersion property of the fine particles in the fine particle dispersion solution by controlling pH of the fine particle dispersion solution obtained after the removal process.